<?php 

class CaptchaSecurityImages {

	protected $font = '/public/fonts/%s%.ttf';

	public function generateCode($characters)
	{
		/* list all possible characters, similar looking characters and vowels have been removed */
		$possible = '23456789bcdfghjkmnpqrstvwxyz';
		
		$code = '';
		$i = 0;
		
		while ($i < $characters) { 
			$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
			$i++;
		}
		
		return $code;
	}

	public function __construct($params = array())
	{
		$width  = (array_key_exists('width', $params) && intval($params['width']) > 0) ? intval($params['width']) : 120; 
		$height = (array_key_exists('height', $params) && intval($params['height']) > 0) ? intval($params['height']) : 40;
		$characters = (array_key_exists('characters', $params) && intval($params['characters']) > 0) ? intval($params['characters']) : 6;
		$this->font = str_replace('%s%', $params['font'], $this->font);
		
		$code = $this->generateCode($characters);
		
		/* font size will be 75% of the image height */
		$font_size = $height * 0.55;
		$image = @imagecreate($width, $height) or die('Cannot initialize new GD image stream');
		
		/* set the colours */
		$background_color = imagecolorallocate($image, 255, 255, 255);
		$text_color  = imagecolorallocate($image, 255, 40, 0);
		$noise_color = imagecolorallocate($image, 100, 120, 180);
		
		/* generate random dots in background */
		for( $i = 0; $i < ($width * $height) / 3; $i++) {
			imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
		}
		
		/* generate random lines in background */
		for( $i = 0; $i < ($width * $height) / 150; $i++) {
			imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);
		}
		
		/* create textbox and add text */
		$textbox = imagettfbbox($font_size, 0, $_SERVER['DOCUMENT_ROOT'] . $this->font, $code) or die('Error in imagettfbbox function');
		$x = ($width - $textbox[4]) / 2;
		$y = ($height - $textbox[5]) / 2;
		
		imagettftext($image, $font_size, 0, $x, $y, $text_color, $_SERVER['DOCUMENT_ROOT'] . $this->font , $code) or die('Error in imagettftext function');
		
		/* output captcha image to browser */
		header('Content-Type: image/jpeg');
		imagejpeg($image);
		imagedestroy($image);
		
		$_SESSION['security_code'] = $code;
		//set_cookie('security_code', $code, '', '', '', '' );
	}
}